354 DKECIOUS MOLLUSCA. 



loose, was moved by the waves, and the young in the eggs 

 had their blood aerated through the membrane, and when 

 hatched they remained defended from the violence of the 

 sea till their shells had not only been formed but had ac- 

 quired strength."* 



These egg-capsules are so diversified in their forms and 

 mode of aggregation, f that M. A. Lund, a learned Danish 

 zoologist, has reduced them into classes and orders in a 

 manner well calculated to impress distinctly their diversity 

 on the memory. The arrangement is as follows : 



CLASS I. 



THE MASS OF EGG-CASES IRREGULAR. (The egg-cases 

 form in their aggregate masses of indeterminate shape.) 



ORDER i. Egg-cases coherent : The cases are attached to 

 and upon each other. 



Family 1. The egg-case opening by a fissure 

 of the margin. 



2. The egg-case opening by a circular 

 aperture furnished with a membra- 

 nous lid. 



ORDER ii. Egg-cases adherent : The cases are attached 

 to a common basal membrane, by which 

 they are rooted. 



Family 1. The egg-case opening by a fissure 

 of the margin. 



2. The egg-case opening by a circular 

 aperture furnished with a membranous lid. 



* The egg-cases sessile, or directly at- 

 tached to their common base. 

 a. Tubiform. 



** The egg-cases pedunculated, or attach- 

 ed to their common base by a pedicle. 



a. Egg-shaped. 



b. Cup-shaped. 



c. Funnel-shaped. 



* Comp. Anat, iii. 396, 



f The various Tubularia represented by Esper in his " Pflanzenthiere," 

 in plates 11 to 16, and 18 to 26, are the egg-cases or embryo sacs of 

 zoophagous mollusca. 



